Preparation of zein solutions directly from gluten



Patented Nov. 6, 1945 UNITED STATES PATENT OFFICE PREPARATION OF ZEINSOLUTIONS DIRECTLY FROM GLUTEN Roy E. Coleman, Chicago, Ill., assignorto Time,

Incorporated, a corporation oi New York No Drawing. Original applicationNovember 30, 1942, Serial No. 467,402, now Patent No. 2,352,604, datedJuly 4, 1944. Divided and this application October 25, 1943, Serial No.507,601

Claims.

Heretofore, in the preparation of zein solutions and coatingcompositions, including the substantially non-aqueous zein solutions andcoating compositions of controlled so.ution and gelling characteristicsas described in my prior Patent No. 2,185,110, granted December 26,1939, for example, the zein is initially isolated from corn gluten andthen dissolved in suitable solvents to form the desired solutions. Toisolate zein from corn gluten as a commercially usable powder is alaborious and expensive process, involving steps of precipitation,settling, filtering, washing and drying. The solubility of the zein inzein solvents and the solution characteristics such'as stability andgelling tendencies are largely dependent upon the care exercised incarrying out the steps of the process.

In accordance with the present invention'Iprepare solutions of zein orzein-containing proteins directly from corn gluten under conditions thatwill readily produce a wide variety of zein products in so far asproperties and solubility characteristics are concerned, and therebyavoid the expense and objections incident to the preliminary isolationof zein in powder form. In carrying out the present invention, corngluten, for example,

in granular or powdered form, is treated with a suitable relatively lowboiling point zein protein solvent or mixture of zein protein solvents,without the establishment of special conditions of hydrogen ionconcentration either in the solvent or in the gluten, to extract thezein from the gluten. The extraction is carried out at elevated scribedis now separated from the residual gluten by filtration, pressing,centrifugal separation or in any other desirable manner, mixed with arelatively high boiling point zein base solvent to be hereinafterdescribed and distilled or otherwise treated to remove all or some ofthe relatively low boiling point solvent, as desired.v The resultingresidue is a solution of zein or zein-containing protein in the zeinbase solvent alone with all of the relatively low boiling point solventremoved, or in the zein base solvent and that portion of the relativelylow boiling point solvent which has not been removed. The residualgluten, whichv still contains some protein, may be freed from retainedsolvent by washing and recovered ior iurther use as a cattle food or forother purposes.

The resulting zein or zein-containing solutions in accordance with thepresent invention, over a wide range of concentrations, are stable onstanding at temperatures of 80 F. and below and do not separate evenwhen cooled to temperatures of 50 to 70 F. and somewhat below. Whencooled even to temperatures as low as 10 above zero or to zero,solutions prepared in accordance with the present invention may separateand become solid; however, on heating again to temper-- atures of iromabout 45 to 70 F., a resolution is temperatures, say from about to about170 F., preferably between about to about F., for a short period of timegenerally not exceeding about three hours. It is preferred that theextraction time be not longer than about one-hall to about one hoursince within this time and at the temperatures stated, the zein in thegluten is extracted and is not deleteriously affected.

The extract solution obtained as above deeffected, either withoutstirring or with slight stirring, and the solutions return to theirnormal. form atthe re-heating temperatures. In general, these solutionsaresubstantially non-gelling and have but a slight'tendency to increasein viscosity; that is, to thicken or become heavier in body. In manyinstances they exhibit practically no tendency to thicken or to gel overpractical periods of time in the order of about 3 to 6 months and evenup to one year and longer. These solutions remain stable and reasonablyconstant in their characteristics during the periods necessary fortransportation and distribution, either in bulk or in packages, or forstorage'ior reasonable periods of time, and hence their field ofapplicability is greatly increased. 8

The protein content of gluten varies widely, depending largely upon thesource of the gluten and the method of making it or obtaining it as aby-product. In the case of corn gluten now on the market, the proteincontent varies from about 40% to 70%. Of this protein content, about 50%to 70% is aqueous-alcohol soluble and is extractable as zein orzein-containing proteins. The amount of zein or zein-containing proteinsextracted in accordance with the methods of the present invention islargely influenced by the 55 particular solvent or solvent mixture usedto the prolamine in the resulting stable solution.

For example, using a corn gluten containing 60% of protein with anestimated extraction of 65%, 39 lbs. of zein are available in 100 lbs.of the gluten. On the basis of producing a final solution in a basesolvent of a solids content of 20%, then 156 lbs. of base solvent willbe required for each 100 lbs. of gluten, providing the estimated amountof soluble protein is extracted. evident thatthe protein content of theextract solution may be determined prior to the admixture of basesolvent with the extract solution, thereby making possible thedetermination of the precise amount of base solvent to be added to theextract solution to obtain the desired concentration of zein protein inthe final solution.

The zein protein extracting solvents in accordance with the presentinvention may be, suitably, a single solvent or a solvent mixture whichis a solvent for zein or other prolamine and which has a boiling pointbelow about 125 C. and, preferably, of about 100 C. and below. Thus, theextracting solvent may be one or more of the weli -kn'own alcoholic zeinsolvents such as anhydrous methanol, or constant boiling point mixtures(azeotropes) of aliphatic alcohols such as 95% ethyl alcohol and 91%isopropyl alcohol. For convenience herein I term these alcoholicsolvents conventrated alcohol solvents. The extracting solvents may alsobe one or more of the concentrated alcohol solvents containingadditional amounts of water, say from 40% to 50% in anhydrous methanolor in excess of that present in the azeotropes 95% alcohol and 91%isopropyl alcohol. Greater or lesser amounts of water than as stated maybeused; however, best results are obtained with the use of added amountsof water within the percentage range stated. For convenience herein Iterm these alcoholic solvents "aqueous alcohol mixtures.

Another class of extracting solvents in accordance with the presentinvention comprises mixtures oi! an azeotropic concentrated alcoholsolvent with a non-solvent and water. Examples of such solvents'aremixtures of 95% ethyl alcohol or 91% ispropyl alcohol withdichlorethylene, trichlorethylene, ethyl acetate, benzene, cyclohexane,etc., and water. In this class of extracting solvents I also includemixtures of 95% alcohol and non-solvents as disclosed in my prior PatentNo. 2,185,123, granted December 26, 1939, and non-aqueous azeotropicmixtures of anhydrous methyl alcohol with hexane, cyclohexane, benzene,carbon tetrachloride, dichlorethylene, trichlorethylene, acetone, methylacetate, ethylacetate, methyl ethyl ketone, etc., because oneconstituent of the mixture, methyl alcohol, is a zein solvent.

In addition to the foregoing, wherein at least one constituent of anextracting solvent mixture is a zein solvent, the extracting solventsmay be suitable azeotropic mixtures which are zein protein solventswherein theindividual constitassaaao uents oi the mixture arenon-solvents tor zein proteins. Thus, they may be azeotropic mixturesdioxan boiling at 86.9 C.; and butyl alcohol It is forms with water aconstant boiling point mixture containing 63% butyl alcohol boiling at92 C.

In general, extracting solvents consisting of or including the aqueousalcohol mixtures ar capable of extracting larger amountsv of zein,

protein from gluten than are the extracting solvents consisting of orincluding a concentrated alcohol solvent. It has been noted that forpractical extraction procedures, using either a concentrated alcoholsolvent alone or an aqueous alcohol mixture alone, approximately 2 partsby weight of solvent to 1 of gluten may be used. At this concentration,with gluten containing approximately 60% total protein, the extractsolutions of the concentrated alcohol solvent contain a maximum zeinprotein content of approximately 10% whereas the extract solutions ofthe aqueous alcohol mixture solvents contain a maximum zein proteincontent of from about 12% to about 15% and even up to 20%. In addition,the aqueous alcohol mixture solvents are capable of extracting asubstantially larger proportion oi. a desirable type of zein present inthe protein of the gluten than are the concentrated alcohol solvents.

The base solvents are relatively high boiling compounds or mixtures ofcompounds having a boiling point above about 0., preferably above aboutC. and having a suitable balance between the hydrocarbon constituents orradicals present in the solvent or solvent mixtures and the polarconstituents or radicals present therein. A certain proportion ofhydroxyl radicals in the base solvents is required to secure andmaintain solvent action. Other polar radicals such as -O-(ether oxygen),-C1, -NH: and COOH were intermediate the methyl and ethyl radicals.

This range is approximate and may vary somewhat depending on the solventor solvent mixture used. The limits of this range are indicative ofsolvent properties and provide a close and adequate guide to'enable theoperator, by simple experimentation, to determine the required balanceof polar and hydrocarbon radicals in the base solvent or mixture of basesolvents in accordance with the present invention.

It may be stated that the base solvents in accordance with the presentinvention may be any one of the solvents or mixture of solventsdescribed in my prior Patent No. 2,185,110 which has the requiredbalance of polar and non-polar radicals, and a boiling point above about125 0., preferably, above about 150 C. as pointed out above. For a morecomplete description of the kinds of solvents which may be used as baseused in accordance with solvents in accordance with the presentinvention than is disclosed herein. reference is made to the descriptionof these solvents in my prior Patent No. 2,186,110.

Examples of base solvents in accordance with the present invention arethe glycols such as diethylene' glycol, propylene glycol, triethyleneglycol and mixtures thereof, including mixtures which contain ethyleneglycol; 'diacetone alcohol; closed chain cyclic alcoholssuch as benzylalcohol, cyclohexanol, furfuryl alcohol, tetrahydrofurfuryl alcohol andmixtures of closed chain alcohols; glycol ethers such as ethylene glycolmono-methyl ether, diethylene glycol monomethyl ether, ethylene glycolmono-ethyl ether, diethylene glycol monoethyl and mixtures of glycolethers; mixtures of two or more of the foregoing enumerated basesolvents; mixtures of one or more of the foregoing base solvents withglycerine, or other-solvents or mixtures of solvents, providing themixture has the required polar to non-polar radical balance and therequired relatively high boiling point. It isfto be understood that theforegoing speciflcaliymentioned solvents or mixtures of solvents are notintended to be inclusive of all the base solvents which may be thepresent invention since they are merely set forth for illustrativepurposes.

Zein or zein-containing extract solutions containing any one or more ofthe foregoing base solvents, in accordance with the present inventionmay be foiled, distilled or otherwise treated to remove part or all ofthe diluent. It is evident that practically all of the extractingsolvent, ineluding any water carried from the gluten to the extractsolution. may be removed, thereby obtaining solutions of zein orzein-containing proteins,

in the base solvent which, for all practical purposes, are substantiallyanhydrous. Such solutions vary widely in character, depending upon thechoice of solvents or solvent mixtures used,

as is to beexpected, and some of them may undergo changes (apparentinsolubili-ty. for exam- 5 pie) during the solvent and water removalwhich effect the solvent characteristics of the zein and zein-containingproteins in the base solvent utilized. These changes, where they takeplace, are not of a permanent character and it is possible to eifect are-solution of the zein or zein-containing proteins in the base solventsby the addition oi a small amount of water, say in the order of fromabout 1 to 3% by weight, or an equivalent amount of other highlyhydroxylated compound, such as methyl or ethyl alcohol or a mixture ofsuch compounds. 7

In the preparation of usable solutions having a wide field ofapplicability, I prefer that the removal of the relatively low boilingpoint sol- 6 vent and water be controlled so asto leave in the finalsolutions at least about 1 to 3% by weight of water or an equivalentamount of other highly hydroxylated compound, preferably water. Wherethis is not possible, water may be added 6 to the final solution, in theamounts stated. While water is, in general, not an essential constituentof some of the solutions formed in accordance with the presentinvention, the solutions are generally of an improved character whenthey contain small amounts of water. The solutions may contain largeramounts of water, say between 5 to 10%. or even more.

As already pointed out, the type or character or the zein-containingprotein produced by the 76 which generally produces solutions extractionis in no small part dependent on the character of the extractionsolvents used. This condition is particularly pronounced when the highlyaqueous alcohols or the high water azectropes such as dioxan-water orn-butyl alcoholwater mixtures are used as solvents. Not only do thesesolvents effect the extraction of a larger amount of the zein-containingprotein than do the more concentrated alcohols, butthey also produce bytheir extraction a type of zein protein having a high viscosity andpronounced colloidal consistency. On the other hand the zein proteinproduced with the concentrated alcohols and less aqueous diluents tendsto produce solutions having a lower viscosity and a lesser colloidalconsistency. It is thus evident that various types of zein proteinhaving substantially different properties can be produced by properselection and composition of the extracting solvents.

From the foregoing it is manifest that the nature and properties of thefinished solution will be determined by the amount of zein proteinpresent in the solution, the type or character of the zein proteinextracted by the particular extracting solvent used and by the nature ofthe base solvent. It is apparent that with the extracting solvent andbase solvent combinations possible, a wide variety of solutions for manyuses can be produced by the method of the present inven- 131011;

Within the range of the many possible combinations and the method inaccordance with the present invention, solutions may be produced whichrequire further adjustment or modification in order to secure improvedsolution or desired stability and controlled gelling properties. Suchadjustments or modifications can be readily effected by the use ofresin, fatty acids, compatible amines suchas monoethanolamine,triethanolamine, etc., amine soaps of rosin or fatty acids, or by thevarious methods and materials for producing stable, controlled gelling,zein solutions described in my issued Patents Nos. 2,185,122; 2,246,779and 2,298,548. The addition of suitable materials for eifecting desiredmodiflcation or adjustment may be made to the extract solutioncontaining the base solvent before distilling ofl .the extractingsolvent or to the final solution. The preferable procedure and materialswith particular solutions may be easily determined by experimentation.

In the following examples I disclose illustrative methods for producingzein or zein-containing solutions directly from gluten in accordancewith the present invention. In the examples and elsewhere throughout thespecification, the term "parts" indicates parts by weight.

I Example 1.600 parts of 91% isopropyl alco- 0 hol were added to partsof powdered gluten in a vessel. The mixture was heated to about F. andheld at about that temperature for about /2 hour with stirring toextract the zeincontaining proteins from the gluten. The mix- 5 ture wasthen forced through a filter to separate the zein-containing extract. To100 parts of the extract 40 parts of propylene glycol were added and themixture was slowly'heated to about 250 F. and held at about thattemperature with stirring until cessation of visible boiling. Theresidue was a solution of zein-containing proteins principally inpropylene glycol.

In the following examples the manipulative procedures were the same asset forth in Example 1 except that the extractions were carried extract.The procedure sisting of 63% Example 2.-'75 parts of powdered glutenwere extracted with 187 parts of a solvent mixture consisting of 70% ofdenatured 95% ethyl alcohol (Synasol"), and 30% of water. 29% parts ofdiethylene glycol were added to 50 parts of the was as in Example 1 wasa solution of zeinin diethylene glyand the resulting solution containingproteins principally col.

Example 3.--29/ parts of propylene glycol were added to 50 parts of theextract of Example 2. The procedure was as in Example 1 and theresulting solution was a solution of zein-containing proteinsprincipally in propylene glycol.

Example 4.-29 /2 parts of diethylene glycol monoethyl ether were addedto 50 parts of the extract of Example 2. The procedure was as in Example1 and the resulting solution was a solution of zein-containing proteinsprincipally in diethylene glycol monoethyl ether.

Example 5.-30 parts of powdered gluten were extracted with 75 parts of asolvent mixture consisting of 80% of dioxan and of water. parts ofethylene glycol monoethyl ether were added to 47 parts of the extract.The procedure was as in Example 1 and the resulting solution was asolution of zein-containing proteins principally in ethylene glycolmonoethyl ether.

Example 6.-30 parts of powdered gluten were extracted with '15 parts ofa solvent mixture conof n-butyl alcohol and 37% of water. 19.3 parts ofbenzyl alcohol were added to 44 parts of the extract. The procedure wasas in Example 1 and the resulting solution was a solution ofzein-containing proteins principally in benzyl alcohol.

Example 7.-20 parts of powdered gluten were extracted with 50 parts of asolvent mixture consisting of 60% of 91% isopropyl alcohol and 40% ofwater. 17 /2 parts of diethylene glycol were added to parts oftheextract. The procedure was as in Example 1 and the resulting solutionwas a solution of zein-containing proteins principally in diethyleneglycol.

At the cessation of boiling as referred to in the examples someproportion of the lower boilln constituents of the diluent originallyused remains in the final solution. The proportion thereof so remainingdepends upon the final temperature and the boiling point curve of themixture. Considerable proportions of the diluent or of its constituents,including water, may remain without causing gelling of the finalsolution in reasonable periods of time. This is particularly true wherethe glycols are used. In this respect the final solutions showdifferences from solutions of commercial zein containing large amountsof water as in ently by reason of some changes in the character orstructure of the zein-containing proteins of the corn gluten takingplace in the process of the present invention, the nature of whichchanges is not as yet understood.

In general and influenced by the type and amount of zein proteinpresent, the solutions prepared as described above and the coatincompositions prepared therefrom have the properties, particularly whenheated, of being able to give up" their solvent or solvents readily, andwhen applied to a surface they quickly and tion of polar to nonthe priorart, apparreadily form tough, flexible, non-tacky, hard and generallytransparent coatings even when retaining some solvent. The coatingsformed by these zein-containing solutions and coating compositions arevery strong and have adherent properties. In these solutions and coatingcompositions the film forming properties thereof can bebuilt up toproduce films or great toughness, flexibility, hardness and glOSS. Undernormal temperature conditions, many of the zein containing solutions orcoating compositions will produce non-blushing coatings on drying,without the aid of supplementary anti-blushing agents as in the priorart.

The coating compositions prepared from the above solutions may bemodified and used as fully described in the aforementioned applicationSerial No. 467,402, now Patent No. 2,352,604. granted July 4, 1944.

While my invention has been described in connection with certainspecific examples, it is, of course, obvious that it is not to beconstrued as limited to these examples or to the details of the methodsset forth therein, since obvious changes in materials, proportions andmethod details will be apparent from the foregoing.

In the claims, the expression an elevated temperature in the order-ofabout F. to about 170 F. is not to be construed as a precise criticalrange, but, rather, as a range of temperatures indicative of theelevated temperature at which the extractions may be carried out.

I claim:

1. The method of preparing directly from gluten a solution ofzein-containing proteins in a solvent or mixture of solvents comprisinga an essential solvent constituent for the zein-containing proteins, asolvent havin a boiling point above about C. and having a proporlarradicals which lies within a range extending between the limits of theproportion of polar to non-polar radicals of methanol and the proportionof polar to nonpolar radicals of ethanol, which comprises contactinggluten with a zein protein solvent having a boiling point below about125 C. at an elevated temperature in the order of about 120 F. to about170 F. to extract zein-containing proteins from the gluten, said zeinprotein solvent comprising an azeotropic mixture, the constituents ofwhich are individually non-solvents for said proteins, separating theextract solution from the residual gluten, mixing the aforesaid solventhaving a boiling point above about 125 C. with said extract solution andremoving at least part of said relatively low boiling point solvent fromthe solution.

2. The method of preparing directly from gluten a solution ofzein-containing proteins in a solvent or mixture of solvents comprisingas an essential solvent constituent for the zein-containing proteins, asolvent having a boiling point above about C. and having a. proportionof polar to non-polar radicals which lies within a range extendinbetween the limits of the proportion of polar to non-polar radicals ofmethanol and polar radicals of ethanol, which comprises contactinggluten with a zein protein solvent having a boiling point below about125 C. at an elevated temperature in the order of about 120 F. to aboutF. to extract zein-containing proteins from the gluten, said zeinprotein solvent comprising an azeotropic' mixture, the constituents ofwhich are individually non-solvents for the proportion of polar to non-'said proteins, separating the extract solution from the residual gluten,mixing a zein-contain ing protein solvent comprising the aforesaidsolvent having a boiling point above about 150 C. with said extractsolution and removin substantially all of said relatively low boilingpoint solvent from the-solution.

3. The method of preparing directly from gluten a solution ofzein-containing proteins in a solvent or mixture of solvents comprisingas an essential solvent constituent for the zein-containing proteins, asolvent having a boiling point above about 150 C. and having aproportion of polar to non-polar radicals which lies within a rangeextending between the limits of the proportion of polar to non-polarradicals of methanol and the proportion of polar to non-polar radicalsofethanol, which comprises contacting gluten with a zein protein solventhaving a boiling point below about 125 C. at an elevated temperature inthe order of about 120 F. to about 170 F. to extract zein-containingproteins from the gluten, said zein protein solvent comprising anazeotropic mixture, the constituents of which are individuallynon-solvents for said proteins, separating the extract solution from theresidual gluten, mixing a zein-containing protein solvent comprising theaforesaid solvent having a boiling point above about 150 C. with saidextract solution and removing at least part of said relatively lowboiling point solvent from the solution.

4. The method of preparing directly from gluten a solution ofzein-containing proteins in a solvent or mixture of solvents comprisingas an essential solvent constituent for the zein-containing proteins, asolvent having a boiling point. above about 150 C. and having aproportion of polar to non-polar radicals which lies within a rangeextending between the limits of the proportion of polarto non-polarradicals of methanol and the proportion of polar to non-polar radicalsof ethanol, which comprises contacting gluten with a zein proteinsolvent having a boiling point below about 100 C. at an elevatedtemperature in the order of about 120 F. to about 170 F. to extractzein-containing proteins from the gluten, said zein protein solventcomprising an azeotropic mixture, the constituents of which areindividually non-solvents for said proteins, separating the extractsolution from the residual gluten, mixing a zein-containing proteinsolvent comprising the aforesaid solvent havin a boiling point aboveabout 150 C. with said extract solution and removing at least part ofsaid relatively low boiling. point solvent from the solution.

5. The method of preparing directly from gluten a. solution orzein-containing proteins in a solvent or mixture of solvents comprisinga glycol ether as an essential solvent constituent for thezein-containing proteins, which comprises contacting gluten with a zeinprotein solvent having a boiling point below about 100 C. at an elevatedtemperature in the order of about 120 F. to about 170 F. to extractzein-containing proteins from the gluten, said zein protein solventcomprising an azeotropic mixture, the constituents of which areindividually non-solvents for said proteins, separating the extractsolution from the residual gluten, mixing a zein-containing proteinsolvent comprising a glycol ether with said extract solution andremoving at least part of said relatively low boiling point solvent fromthe solution.

6. The method of preparing directly from gluten a solution ofzein-containing proteins in a solvent or mixture of solvents comprisinga glycol ether as an essential solvent constituent for thezein-containing proteins, which comprises contacting gluten with a zeinprotein solvent having a boiling point below about 125 C. at an elevatedtemperature in the order of about F. to about 170 F. to extractzein-containing protein from the gluten, said zein protein solventcomprising an azeotropic mixture, the constituents of which areindividually non-solvents for said proteins, separating the extractsolution from the residual gluten, mixing a zeincontaining proteinsolvent comprising a glycol ether with said extract solution andremoving at least part of said relatively low boiling point solvent fromthe solution.

7. The method of preparing directly from gluten a solution ofzein-containin proteins in a solvent or mixture of solvents comprisingethylene glycol monoethyl ether as an essential solvent constituent forthe zein-containing proteins, which comprises contacting gluten with azein protein solvent having a boiling point below about C. at anelevated temperature .in the order of about 120 F. to about F. toextract zeincontaining proteins from the gluten, said zein proteinsolvent comprising an azeotropic mixture, the constituents of which areindividually non-solvents for said proteins, separating the extractsolution from the residual gluten, mixing a zein-containing proteinsolvent comprising ethylene glycol monoethyl ether with said extractsolution and removing at least part of said relatively low boiling pointsolvent from the solution.

8. The method of preparing directly from gluten a solution ofzein-containing proteins in a solvent or mixture of solvents comprisingbenzyl alcohol as an essential solvent constituent for thezein-containing proteins, which comprises contacting gluten with a zeinprotein solvent having a boiling point below about 125 C. at an elevatedtemperature in the order of about 120 F. to about 170 F. to extractzein-containing proteins from the gluten, said zein protein solventcomprising an azeotropic mixture, the constituents of which areindividually non-solvents for said proteins, separating the extractsolution from the residual gluten, mixing a zeincontaining proteinsolvent comprising benzyl al cohol with said extract solution andremoving at least part of said relatively low boiling point solvent fromthe solution.

9. The method of preparing directly from glu ten a solution ofzein-containing proteins in a solvent or mixture of solvents comprisingethylene glycol monoethyl ether as an essential solvent constituent forthe zein-containing proteins, which comprises contacting gluten with arelatively low boiling point zein protein solvent comprising anazeotropic mixture of dioxan and water at an elevated temperature in theorder oi. about 120 F. to about 170 F. to extract zeincontainin proteinsfrom the gluten, separating the extract solution from the residualgluten, mixing a zein-containing protein solvent comprising ethyleneglycol monoethyl ether with said extract solution and removing at leastpart of said relatively low boiling point solvent from the solution.

10. The method of preparing directly from gluten a solution ofzein-containing proteins in a solvent or mixture of solvents comprisingbenzyl alcohol as an essential solvent constituent for taining proteinsfrom the gluten, separating the the zein-contalning proteins, whichcomprises extract solution from the residual gluten, mixing contactinggluten with a relatively low boiling a zein-containing protein solventcomprising benpoint zein protein solvent comprisin an azeozyl alcoholwith said extract solution and retroplc mixture of n-butyl alcohol andwater at 5 moving at least part of said relatively low boilan elevatedtemperature in the order of about ing point solvent from the solution.120 F. to about 170 F. to extract zein-con- ROY E. COLEMAN.

